1. Field of the Invention
The present invention relates to a side airbag device for vehicle.
2. Description of Related Art
Japanese Patent Application Publication No. 2000-177527 (JP 2000-177527 A) discloses a constitution that includes a side airbag in which an upper chamber and a lower chamber, which are different in internal pressure each other during inflation and deployment, are disposed in a vehicle vertical direction in a seat back of a vehicular seat. Specifically, a gas generator and the side airbag that is constituted of the upper chamber that is made expandable at the side of a chest region of an occupant and the lower chamber that is made expandable at the side of a pelvis of the occupant are disposed in the seat back. The upper chamber and the lower chamber are filled with a gas by the gas generator such that internal pressures in the respective filled states are different and are made expandable.
According to the constitution described above, during a vehicle side collision (hereinafter, referred to as “side collision”), the gas is filled in the upper chamber and lower chamber from the gas generator, and impact to a chest region and pelvis of the occupant can be alleviated thereby. At this time, when the internal pressure of the upper chamber disposed at the side of the chest region is set lower than the internal pressure of the lower chamber disposed at the side of the pelvis, the impact to the chest region that is relatively weak to load can be alleviated by the upper chamber of low load.
On the other hand, Japanese Patent Application Publication No. 2003-285709 (JP 2003-285709 A) discloses a constitution in which a first side airbag device is disposed in a seat cushion of a vehicular seat, and a second side airbag device is disposed in a seat back. Specifically, this constitution includes the first side airbag that is disposed on the seat cushion side and protects a lumbar part and a part lower than that of an occupant, and the second side airbag that is disposed on a seat back side, protects an abdominal part and a part higher than that of the occupant, and is provided with a vent hole.
According to the constitution described above, when the first side airbag and second side airbag are deployed during the vehicle side collision, since the first side airbag is not provided with the vent hole, the internal pressure is maintained at a high level. Thus, the lumbar part and the part lower than that of the occupant can be moved to a non-collision side. On the other hand, in the second side airbag, since the vent hole is provided, the internal pressure decreases. Thus, the chest part and the like of the occupant can be protected with the second side airbag of low load.
Further, Japanese Patent Application Publication No. 2008-094235 (JP 2008-094235 A) discloses a constitution in which a side airbag of which stiffness is different in a vehicle longitudinal direction is disposed in a seat cushion of a vehicular seat. Specifically, this constitution includes a side airbag for lumbar part for absorbing a shock energy to the lumbar part by restraining the lumbar part of an occupant, and a side airbag for thigh part which has the stiffness or the like different from the side airbag for lumbar part and absorbs the shock energy to the thigh part by restraining the thigh part. Further, the stiffness of the side airbag for thigh part is set higher than that of the side airbag for lumbar part.
According to the constitution described above, when the side airbag for lumbar part and the side airbag for thigh part are deployed under a gas supply from the gas generator during the vehicle side collision, the internal pressure of the side airbag for thigh part becomes higher than the internal pressure of the side airbag for lumbar part. As a result, by the side airbag for thigh part of which stiffness is set higher, the thigh part of the occupant is restrained. Therefore, a pubic bone load that is input particularly to the pubic bone part of the lumbar part of the occupant can be reduced with a small energy absorption stroke.
However, when the constitution disclosed in JP 2000-177527 A is used, the side airbag having the upper chamber and the lower chamber is disposed in the seat back of the vehicular seat. That is, since there is a relatively long distance from the side airbag to the lumbar part of the occupant seated on the vehicular seat, there is a room for improvement from the viewpoint of improving the restraining property of the lumbar part of the occupant (first problem).
Further, since the side airbag is disposed at the side of chest part, there is a room for improvement of the restraining performance of the lumbar part and a part lower than that of the occupant, in particular, the pubic bone part and femur bone that are near a seat surface of the seat cushion (second problem).
Further, there is a room for improvement from a point that the side airbag that restrains the lumbar part of the occupant is controlled to optimum internal pressures in accordance with immunity values to loads of the respective sites of the occupant. That is, there is a room for improvement from a point that at the pubic bone part and femur bone that are relatively high in the immunity value to the loads and an iliac bone part that is relatively low in the immunity value, the side airbag is controlled to the optimum internal pressures in accordance with the immunity values of the respective sites. Further, the same can be said regarding the lumbar part that are relatively high in the immunity value to the load and the abdominal part that is relatively low in the immunity value (third problem).
On the other hand, according to the constitution disclosed in JP 2003-285709 A, the first side airbag device is constituted to be disposed in the seat cushion. Therefore, the first problem and second problem can be solved. However, the third problem still remains in an unsolved state. That is, the pubic bone part and femur bone that are relatively high in the immunity value and the iliac bone part that is relatively low in the immunity value are restrained by the first side airbag device having the same internal pressure. Further, since the first side airbag device is not provided with the vent hole, the internal pressure of the side airbag is maintained at a high level. Therefore, the iliac bone part is restrained by the side airbag having high internal pressure.
Further, in the case when the constitution disclosed in JP 2008-094235 A is used, since a constitution in which the side airbag for thigh part and the side airbag for lumbar part are disposed, and the side airbag for thigh part is set to higher internal pressure than that of the side airbag for lumbar part is adopted, the third problem can be solved. However, the side airbag for thigh part disposed on a front side in the vehicle longitudinal direction is constituted to be high in the internal pressure. Therefore, when an occupant is out of position, there is a room for improvement from the viewpoint of suppressing an influence on the occupant.